There are various furnaces which are heated with induction coils for example. One example is known from the international patent application with publication number WO09010086A1, which is also published as U.S. patent application publication no. 2010-181538, which is hereby incorporated herein by this reference for all purposes. A further example is set out in European patent EP 1495276 B1, which is also published as US patent application publication no. 2005-185692, which is hereby incorporated herein by this reference for all purposes.
It has been found that problems with the reliability of such induction furnaces can occur if very high temperatures are present over a longer period of time or if very aggressive materials are released in the furnace. For example, oxygen released from the material to be converted can attack the furnace wall. There are therefore attempts to prevent oxygen reaching the interior of the furnace in the first place. An example of this is known from the international patent application with the publication number WO09010100A1, which is also published as US patent application publication no. 2010-242814, which is hereby incorporated herein by this reference for all purposes. However, even more aggressive are substances containing sulphur and chlorine. Sulphur and chlorine are common constituents of organic materials, e.g. in the case residues or similar.